Check valve



FIG. 1 is a perspective view of a check valve embodying the design of my invention;

FIG. 2 is a top view thereof, which is identical in all respects to a view taken from the bottom of the check valve;

FIG. 3 is a first end view thereof;

FIG. 4 is a side view thereof, which is identical when taken from either side of the valve; and,

FIG. 5 is a second end view thereof. 

The ornamental design for a check valve, as shown and described. 